Microsoft today revealed what's in store for the next-generation of its Windows Phone platform. The company announced Windows Phone 8.1, which succeeds Windows Phone 8. The first new feature revealed by Microsoft is an action center, which mimics the behavior of the notification tray in Android. It provides access to radios, actionable notifications, and other tool. Windows Phone 8.1 adds the ability to personalize the lock screen, which can be interactive and appear in a wide range of styles. Microsoft plans to offer APIs to developers so they can create their own lock screen customization tools. The third new feature is an evolved Start Screen experience. With 8.1, users can choose a high-density layout that includes three columns for tiles, as well as use background images that appear behind all the tiles. Windows Phone also introduces Cortana, a voice-activated search assistant that responds to users' voice commands and questions. Cortana is built on Microsoft's Bing search engine, and can perform searches, schedule appointments, set reminders, and more. Cortana includes several components and can learn users' most-frequently contacted people, places they prefer to go, and even what music they typically search for. Cortana can also be used to set "do not disturb" time, which Microsoft calls Quiet Hours. Like Google Now, Cortana will scan the user's email for things such as flight details, and automatically provide details such as travel times to the airport, flight delays, and more. Microsoft says that Windows Phone 8.1 is also a better choice for business users thanks to new support for secure VPNs, and the ability to read encrypted emails. Devices can be activated by businesses and turned into secure work machines, but can also be stripped of enterprise apps and features if an employee were to leave a company but keep their phone. Windows Phone 8.1 includes significant changes to the Windows Phone Store, such as more personalized recommendations, easier-to-use categories, and quick links. There's a new calendar in WP8.1, which allows users to swipe from day-to-day as well as see "week" views. A feature called Wi-Fi Sense suggests known, good, free Wi-Fi networks that may be available in public spaces - and will automatically connect to them. Microsoft has also added a new keyboard to Windows Phone that allows users to swipe their finger across the keyboard rather than type. Last, Microsoft said Windows Phone includes IE 11 and new synchronization tools that will better share information between the mobile phone and Windows desktops.

Microsoft today also said that Windows Phone 8.1 will first be available on brand new smartphones in late April or early May. Windows Phone 8.1 will be distributed to existing devices "in a few months," according to Microsoft's Joe Belfiore. As always, the timing of Windows Phone 8.1's release to existing hardware will depend on region, carrier, and device. Finally, Microsoft today announced it is making it possible for developers to create a single app that will run on Windows Phones, Windows tablets, and Windows PCs. Microsoft calls these Universal Windows Apps. Microsoft is making this possible with new developer tools thanks to user interface code, APIs, app models, and the Windows Store. Universal apps will be available with Windows Phone 8.1, as well as Windows 8.1 tablet/PC hardware.